water fern

any member of a group of ferns in the subfamily Parkerioideae, family Pteridaceae, plant division Pteridophyta. Ceratopteris consists of at least four species (C. cornuta, C. pteridoides, C. richardii, and C. thalictroides), which are widespread in tropical and warm-temperate regions around the world. Although the plants sometimes root in mud, more frequently they float on the surface of shallow water in ditches, lakes, and sluggish backwaters of riverine environments. Individual plants have dimorphic leaves. They produce a rosette of lettucelike, lobed or divided, vegetative leaves, which often have somewhat inflated petioles (an adaptation to floating). These leaves usually produce small meristematic buds along the margin that give rise to "daughter plants," which are asexual (vegetative) offshoots that eventually grow directly into free-living plants-essentially clones of the initial plant. The fertile leaves of Ceratopteris species are much more finely divided than the vegetative ones, and the narrow leaf segments have the undersurface nearly entirely covered with sporangia. The sporangia are protected in part by the recurved margins of the leaf segments. The spores are globose and trilete.